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Abstract

We demonstrate optical true time delays using wavelength conversion coupled with chromatic dispersion. The transfer function of the delay system is investigated, and it is shown that 3-dB bandwidth of the system can be increased over 40 GHz by using offset pumps. A flat magnitude response (<1 dB peak-peak, 0.2 dB RMS deviation) is achieved in the 1-30 GHz band. Calculated matched filter output to LFM pulses shows good performance, maintaining a > 30 dB peak-to-sidelobe-ratio. The effect of pump depletion during wavelength conversion is also investigated.

Fig. 2 Experimental setup. Spectra at output of the two PPLN waveguides are also shown for configuration B (10 dB/div, 2.5 nm/div). The dashed line is used for case-A only. BPF: bandpass filter, PC: polarization controller

Fig. 7 The calculated matched filter output to the LFM pulse: (a) The actual PPLN W/C transfer functions for carrier optimized and offset pump cases. (b) The 12-hour measurements are used for the complete system for both cases.

Fig. 8 (a) experimental magnitude response measurements when the probe pump, λD, used in PPLN-1 is used in PPLN-2 again. Each data curve is artificially shifted down by 1 dB for clarity purposes. (b) The calculated magnitude response using the model.

Fig. 9 (a) The effect of increasing pump power on the experimental magnitude response of the system. The top curve shows the independent pump result that was given in Fig. 3. (b) The calculated output response for different modulation index of the probe pump.